avrt_wrapper_win.cc revision 5821806d5e7f356e8fa4b058a389a808ea183019 
1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "media/audio/win/avrt_wrapper_win.h"
6
7#include "base/logging.h"
8
9namespace avrt {
10
11// Function pointers
12typedef BOOL (WINAPI *AvRevertMmThreadCharacteristicsFn)(HANDLE);
13typedef HANDLE (WINAPI *AvSetMmThreadCharacteristicsFn)(LPCWSTR, LPDWORD);
14typedef BOOL (WINAPI *AvSetMmThreadPriorityFn)(HANDLE, AVRT_PRIORITY);
15
16HMODULE g_avrt = NULL;
17AvRevertMmThreadCharacteristicsFn g_revert_mm_thread_characteristics = NULL;
18AvSetMmThreadCharacteristicsFn g_set_mm_thread_characteristics = NULL;
19AvSetMmThreadPriorityFn g_set_mm_thread_priority = NULL;
20
21bool Initialize() {
22  if (!g_set_mm_thread_priority) {
23    // The avrt.dll is available on Windows Vista and later.
24    wchar_t path[MAX_PATH] = {0};
25    ExpandEnvironmentStrings(L"%WINDIR%\\system32\\avrt.dll", path,
26        arraysize(path));
27    g_avrt = LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
28    if (!g_avrt)
29      return false;
30
31    g_revert_mm_thread_characteristics =
32        reinterpret_cast<AvRevertMmThreadCharacteristicsFn>(
33            GetProcAddress(g_avrt, "AvRevertMmThreadCharacteristics"));
34    g_set_mm_thread_characteristics =
35        reinterpret_cast<AvSetMmThreadCharacteristicsFn>(
36            GetProcAddress(g_avrt, "AvSetMmThreadCharacteristicsW"));
37    g_set_mm_thread_priority = reinterpret_cast<AvSetMmThreadPriorityFn>(
38        GetProcAddress(g_avrt, "AvSetMmThreadPriority"));
39  }
40
41  return (g_avrt && g_revert_mm_thread_characteristics &&
42          g_set_mm_thread_characteristics && g_set_mm_thread_priority);
43}
44
45bool AvRevertMmThreadCharacteristics(HANDLE avrt_handle) {
46  DCHECK(g_revert_mm_thread_characteristics);
47  return (g_revert_mm_thread_characteristics &&
48          g_revert_mm_thread_characteristics(avrt_handle));
49}
50
51HANDLE AvSetMmThreadCharacteristics(const wchar_t* task_name,
52                                    DWORD* task_index) {
53  DCHECK(g_set_mm_thread_characteristics);
54  return (g_set_mm_thread_characteristics ?
55          g_set_mm_thread_characteristics(task_name, task_index) : NULL);
56}
57
58bool AvSetMmThreadPriority(HANDLE avrt_handle, AVRT_PRIORITY priority) {
59  DCHECK(g_set_mm_thread_priority);
60  return (g_set_mm_thread_priority &&
61          g_set_mm_thread_priority(avrt_handle, priority));
62}
63
64}  // namespace avrt
65